I just listed my car and got a text from a guy in Maryland who wants to buy it. He says the money is coming via PayPal. I get an email saying the money is sitting in an account but I have to pay him first with a $650 Moneygram for the shipping of the car. There's nothing from PayPal reflecting any of this, just emails. Is this a well-known scam?

Yea its well known, they pay you too much of fake money to get you to send some real money back or come up a line of lies to get you to wire money back to them and your out your money. Even in person some have fake money orders that bounce leaving you with fake check charges when it bounces, then your going to Jail. Plus that fake money order is too large for the sale dollar amount your selling for, so they have you (since your cashing it) give them the difference in payment they owe you and the amount the fake money order amount is for, a few weeks later the fake money order bounces hard, then your stuck with no car, owe the bank xxxx amount of money, gone to jail arrested, owe court fees ect ect ect.

SCAM! SCAM SCAM!

It's pretty OBVIOUS that it's a scam.